Velocity changes ($dv/v$) during and after earthquakes are important indicators for understanding the earthquake-induced mechanical damage evolution of rock slopes. However, studying slope responses associated with various seismic loading still remains challenging due to limited in situ observations. In this article, we conduct a 20 min temporal resolution monitoring of $dv/v$ at the frequency band between 2 and 20 Hz by applying ambient noise interferometry on the Pubugou rock slope in Southwest China. We observe an instantaneous ∼0.41% $dv/v$ drop on the slope caused by the 2021 M 7.4 Maduo earthquake at a distance of 780 kM, following a characterized logarithmic recovery process of ∼31.39 h towards its pre-earthquake state. Moreover, the $dv/v$ in five narrow frequency bands show a similar drop and subsequently increased recovery times associated with the deceased frequencies due to the long-distant earthquake shaking. We discuss two possible mechanisms related to the heterogeneous rock slope excited by the long-distant earthquake at a low frequency. The study motivates the damage assessment of the rock slope using in situ $dv/v$ and furthers the understanding of subsurface geological risks under diverse seismic loadings.

Spectral analysis is an effective tool for processing seismic signals, particularly when time-domain characteristics are challenging to capture. In this study, we developed a method using P-wave signals to calculate the power spectrum, enabling the estimation of two spectral parameters—peak frequency and shape factor—for earthquakes recorded by regional seismic networks in the Xiangjiaba (XJB) reservoir area from 2010 to 2015. The temporal evolution of the two spectral parameters was analyzed, revealing that the mean values of individual spectral parameters remain relatively stable despite variations in reservoir water levels. However, a notable increase in the ratio of the shape factor to the peak frequency is observed when the XJB reservoir reaches its maximum water level, suggesting its potential as a precursor indicator for reservoir-induced seismicity (RIS). Furthermore, we performed spatial interpolation on the spectral parameters, and the results show that reservoir impoundment significantly influences the spatial distribution of these parameters. In addition, several regions between the two faults in the tail section of the XJB reservoir exhibit an elevation in the proposed precursor indicator. This study presents a new approach for monitoring and early warning of RIS.